Jose Aldo has accused Conor McGregor of using banned substances before his recent fight against Nate Diaz, repeating previous allegations he has made against the Irishman.

Former UFC featherweight champion Aldo was offered a bout at lightweight at UFC 196 but rejected the opportunity, claiming the Irish fighter was using performance-enhancing drugs.

"The fight was not at featherweight – why would I rematch him in a different weight class with no belt?" Aldo said.

"Now, to make this fight at 155, where he was full of juice in his body, where he hides and nobody tests him, only when he gets to Las Vegas, a week before the fight, and then it's way easier for you to clean the body and fight.

"They offered the fight knowing that I wasn't trained at all. I can't say anything. I can train, beat Frankie Edgar and then know that I've earned my fight for the title again."

Aldo, who will face Edgar for the UFC interim featherweight championship at UFC 200 in July, believes McGregor will eventually step back down to featherweight and has backed Diaz to dominate their second fight.

"Nate wins again," he said. "He's used to this weight. It's really hard to move up in weight and continue winning.

"It's going to be different now that Nate will be more prepared. He can do his thing, anything he wants, from start to end.

"He can slap him, anything, because he will win. It can be faster this time. Nate will prepare, will have enough time, and it can be faster this time."